Intravascular stents are commonly used to maintain patency, opening or spread, of a blood vessel in an attempt to maintain normal blood flow in situation such as stenosis, a constriction of blood vessels due to plaque, calcium, thrombus, and other debris or combination of these. Intravascular stents are typically metallic and self-expanding or balloon expandable. However, cases where the blockage, which is composed of plaque, calcium, and other calculus debris, is severe, cutting into the blockage is required in order to enable the delivery and placement of the stent.
A conventional method for placing a stent into an artery with calcium, plaque, and debris is performed by the following process. The process starts by engaging a guiding catheter into the opening of a blood vessel. Then, a guidewire is chosen to pass through the blood vessel to its distal portion of the vessel. A balloon with surgical blades is then advanced over the wire and placed at the site of the stenosis, blockage or obstruction. The balloon with surgical blades is then inflated using an inflation device. The blades will score the plaque, calcium, and debris that line the intimal wall of the artery. Once a satisfactory scoring of the lumen is achieved, the balloon with surgical blades is then withdrawn into the guiding catheter and taken out over the guidewire.
To prevent collapsing of the plaque debris into the freshly cut area, a stent is chosen to act as internal scaffolding to help bridge the brittle and loose debris. A metal stent is then placed into the freshly cut area by use of the coronary guidewire. A stent of specific size is chosen to match the blood vessel size. Then, stent is inflated using an inflation device. The stent is inflated to its nominal size (the size chosen to match the vessel caliber). Since the stent is mounted to an angioplasty balloon, the stent will expand to a specific size based on what atmosphere the stent balloon is inflated to.
Then, the stent may be post-dilated using a non-compliant angioplasty balloon to ensure good apposition to the blood vessel wall. The post-dilation balloon is taken to slightly higher atmospheric pressures using a balloon inflation device. After a satisfactory lumen size is achieved, and then the post-dilation balloon can be withdrawn into the guiding catheter.
However, using the cutting balloon to cut into the blockage can sometimes lead to serious consequences. A common problem with this procedure is the likelihood of small plaque and debris that are dislodged in the distal blood vessel causing flow obstruction and/or pain for the patient. The debris will float down the artery and block blood flow or cause chest pain. Part of the cause of falling debris in the blood stream is due to the blade edge scoring the intimal wall. This scoring of the intimal wall is accomplished by physically inflating a balloon that has mounted athrotomes or linear and narrow surgical blades on the balloon that when pushed radially outward, expanding the balloon, causes a linear crack or score parallel to the intimal wall of the blood vessel. It is similar to taking a sharp knife and cutting the surface of dried dough crust. The current shape of the cutting balloon is the typical shape of a regular angioplasty balloon except, the balloon has athrotomes or blades of a specific height mounted in the direction of the balloon and longitudinally at four equidistant points on the balloon. The other cause of falling debris in the blood stream is the multiple contacts of the intravascular procedural equipments inside the lumen of the blood vessel.
Moreover, sometimes practitioners cut into artery, causing actual tears in the artery, which will result the diffusion of blood outside the artery. This can lead to a pericardial effusion or effusion of blood around the heart pericardium. When this occurs, the chest has to be pierced with a long needle to go from the outside chest to the inside of the chest cavity to pierce the pericardial sac that surrounds the heart.
The general knowledge and acceptance with intravascular procedures is that, the less the steps, the safer and better the procedure will be. Multi steps processes will elevate the chances of scratching of the intimal wall, cuts, punctures, falling debris, and the like. All these will lead to more serious problems and complications. Therefore, most clinicians prefer “primary stenting”, meaning placement of stent without the use of a cutting balloon or a pre-dilation angioplasty balloon to widen the area to be stented if it is feasible or an option.
Furthermore, most practitioners feel that the more they expand a balloon in a blood vessel (pre-dilate), the better they can pass a stent with ease. However, it could lead to an uneven tearing of the intimal wall of the artery when an angioplasty balloon is used or cutting through the vessel itself in cases where cutting balloons are used.